The exhaustive guide to the Doordash Software Engineer interview (2024)

The Recruiter Phone Screen is a pretty straightforward 30-minute call with a DoorDash recruiter; they typically go over your resume and ask about your past experience after a brief round of introductions.

Expect questions about why you want to work at DoorDash and what you're looking for in your next role. They might throw in a few more behavioural questions, but it's not super intense. It's more about setting expectations and seeing if you're a good fit for the company culture. Plus, they'll also give you an overview of what to expect in the next stages of the interview process.

Our best advice for this round is just be yourself and aim to leave a lasting impression (throw in a memorable nugget that makes you stand out from the rest). Also, make sure to ask them any questions you have about the upcoming interviews. This is a good chance to get a feel for what lies ahead.

• Tell me about yourself and recent projects.
• Why do you want to work for DoorDash?
• Can you provide examples of how you've collaborated with teams in the past?
• What excites you the most about the prospect of joining DoorDash's engineering team?
• How do you handle challenges or setbacks in a project?
• What are your career goals?

The next round is the technical screen—a 60-minute virtual interview with one of their Software Engineers. They use this session to see how you tackle problems and communicate.

At the start, the interviewer will give you the lowdown on themselves and the team they're part of at DoorDash. It's a chance for you to get a feel for who you'll be working with.

Then, they'll hit you with coding problems that mirror what you'd encounter on the job. Recent graduates or entry-level candidates typically go through two of these screenings. They throw a couple of coding challenges at you—involving data structure manipulations, algorithm optimizations, or maybe even some basic system design scenarios to see how you approach problem-solving. These could range from implementing a linked list or a sorting algorithm to designing a simple database schema.

As for experienced folks, they typically face one of these rounds where the interviewer dives deeper into more complex problems, like scalability challenges, performance optimizations, or even architectural design discussions.

The setup is pretty hands-on. DoorDash uses platforms like HackerRank or CodeSandbox.

Two tips here:

• Make sure you talk through your problem-solving process aloud so they can follow your logic.
• And at the end, don't forget to ask questions about the team and the company culture to show you're interested.

Once you're through the technical screen, you move to the virtual interview loop. It's a series of 3-4 rounds, each lasting 60-75 minutes. They throw in 15-minute breaks between sessions to catch your breath.

These rounds cover pretty much everything; you'll face coding challenges, systems design questions, and a couple rounds testing your knowledge of the domain. Finally, you'll have the behavioural round.

Let's discuss each in detail:

System Design and Domain Knowledge

The system design and domain knowledge rounds usually last about 75 minutes in total, but it can vary. Sometimes both rounds are combined, and other times they're split into separate sessions, depending on your skill level.

• If they're separate, the Domain Knowledge round will delve into your previous experiences. You'll talk to the interviewer about a project you worked on, sharing what went well and what didn't. They want to know how you learned from both good and bad experiences, so be upfront and don't shy away from discussing your failures.
• As for the system design segment, they'll delve into your understanding of designing scalable and reliable systems. They might present you with hypothetical scenarios or ask you to design a system on the spot. Don't worry, there's no coding involved. They're more interested in your technical know-how and how well you communicate.

System Design

The System Design round for Software Engineers is quite a crucial one. Essentially, it's about tackling large-scale systems and involves designing an entire service or application while considering factors like scalability, reliability, and usability.

So how do you go about it? 4 tips:

• Once you're presented with a problem or design scenario, start by asking clarifying questions about technical or functional requirements. There's no one-size-fits-all answer expected, but probing questions will guide you towards a solution.
• Then comes the actual designing—you'll be provided with a virtual whiteboard tool to help visualise and diagram your solution, as well as make any necessary calculations.
• Now, the key here is to develop a solid high-level design within the first half hour, so make sure to keep a steady pace and communicate your thought process clearly. We recommend you start with a high-level outline before delving into the nitty-gritty details of different components.
• Once you've completed the design, discuss and refine your design with the interviewer. They may ask to optimise your design for specific constraints or consider alternative approaches.
• How can you determine if the system is functioning correctly?
• Are there any potential bottlenecks within the design?
• How do the various components of the system interact with one another?
• How can the system scale effectively?
• How would you handle an unexpected surge in user traffic?
• Can you outline the failover and recovery mechanisms implemented in the design?

Factor in all that feedback and come up with a design that fulfils all the required performance metrics.

Coding

The coding round consists of two 60-minute sessions, pretty similar to the technical screen. They're again looking at how you tackle problems and communicate your thought process.

3 tips for this round:

• You'll want to be solid on Graphs, Stacks, Queues, Lists, Sets, Arrays, Hash maps, and Heaps. Plus, don't forget Linked lists, Recursion, and Search and Sort algorithms.
• Hit up LeetCode and other coding platforms for practice; practice medium to hard-level questions focusing on algorithms, data structures, and object-oriented concepts.
• Finally, effective communication is key. While talking while coding can be challenging, it's crucial to keep the interviewer engaged in your thought process. Ask clarifying questions, outline your approach before diving into the code, and be open to adjusting your strategy based on their feedback. You can partner with a DoorDash Software Engineer to practise this round collaboratively, so you have a better idea of what to expect and how to tackle twists and turns. Prepfully has several DoorDash Software Engineers who would be happy to help.

Behavioural

• The behavioural round is the final step in the onsite interview, lasting 60 minutes. You'll chat with a manager or another Engineer, focusing on how you align with DoorDash's values and the team you're applying for.
• Make sure you know DoorDash's mission and teams beforehand; it guides everything they do. You don't need to be a DoorDash encyclopaedia, but show some excitement about joining the team. Share examples of how you've lived up to those values, like leading a team or taking smart risks, even if they didn't pan out.
• They're also big on diversity, since they believe it sparks innovation. Check out their efforts in this area and think about how you'd add to the mix. You can take help from a DoorDash employee (senior SWE or managers) who can provide deeper insight into this.
  

System Design

• Design the Quora feed page.
• How would you design an efficient delivery system?
• How would you design and validate an ML model for delivery applications to extend their service?
• Design DoorDash from scratch.
• How would you improve Spotify?
• How would you enhance user engagement on the DoorDash app?
• Design a donation drive system.

Coding

• What do you understand about greedy algorithms?
• Given an array of integers, find a combination of three elements whose sum equals a given value X. If no such combination exists, print -1.
• Write an algorithm to find the largest subarray sum for a given array of integers.
• Write an algorithm to insert a node in a Binary Search Tree.
• Given a sorted array and a number N, how would you find the pair whose sum is closest to N?
• How would you find the level of a node in a binary tree?

Behavioural

• Tell me about a time when you’ve handled conflict.
• How do you contribute to diversity and inclusion?
• Describe a time you took on a challenge.
• Why DoorDash?
• Can you share an experience where you demonstrated leadership skills?
• How do you approach problem-solving in a team environment?
• Describe a project where you had to adapt to unexpected changes.
• Tell me about your project experience.